Re: [Xen-devel] [PATCH v2 2/4] xen: introduce grant_map_exists

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 03.10.14 at 16:50, <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> --- a/xen/common/grant_table.c
> +++ b/xen/common/grant_table.c
> @@ -484,6 +484,36 @@ static int _set_status(unsigned gt_version,
>          return _set_status_v2(domid, readonly, mapflag, shah, act, status);
>  }
>  
> +static bool_t grant_map_exists(struct domain *ld,
> +                        struct grant_table *rgt,

Please constify these if possible.

> +                        unsigned long mfn)
> +{
> +    struct active_grant_entry *act;

And this one too.

> +    grant_ref_t ref;
> +    bool_t ret = 0;
> +
> +    ASSERT(&rgt->lock);
> +
> +    for ( ref = 0; ref != nr_grant_entries(rgt); ref++ )

This loop's worst case iteration count is controlled solely by the
"gnttab_max_nr_frames=" command line option afaict, i.e. for a
large enough specified value this is going to become a security
issue.

> +    {
> +        act = &active_entry(rgt, ref);
> +
> +        if ( !act->pin )
> +            continue;
> +
> +        if ( act->domid != ld->domain_id )
> +            continue;
> +
> +        if ( act->frame != mfn )
> +            continue;
> +        
> +        ret = 1;
> +        break;
> +    }
> +
> +    return ret;
> +}

Apart from it not being very useful to introduce a static function
without consumer, I very much expect this patch on its own to
also cause a build error (unused static function). Please fold this
into the patch adding a consumer of the function.

Jan


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